When a plurality of parts or subassemblies are joined in a composite assembly which is secured by fasteners having threaded members, it is often desirable to tighten such threaded members at each joint until a yield threshold is reached thereat. A continual clamping force or load, similar to that applied by a lock washer, is exerted in this way to insure the integrity of the joint. This is particularly true where structural members are joined in the composite assembly and the yield threshold reached at any joint relates to the male fastener. Hydraulic or pneumatic power wrench mechanisms are commonly utilized for tightening the fasteners which join structural members and circuitry for detecting the yield threshold at such structural joints is well known in the art. Such circuitry includes signal processing means for indicating when the yield threshold of a joint has been reached, as disclosed and claimed in U.S. Pat. No. 4,104,779 and 4,211,120. The signals processed by such circuitry are sensed concurrently and usually relate to the torque applied in tightening the fastener and the angular displacement of the fastener during tightening. In hydraulic power wrench mechanisms, it is conventional to utilize strain gauges disposed on the lever arm through which force is applied to turn the fastener, as the transducer means for sensing the torque. The conventional transducer means for sensing the angular displacement in such hydraulic power wrench mechanisms, is a potentiometer disposed along the turn axis of the wrench head through which torque is applied to the fastener. Because of their location relative to the moving parts of the power wrench mechanism, the strain gauges and potentiometer are subject to a harsh physical environment which results from vibration and exposure to damage, with the potentiometer being particularly vulnerable. Furthermore, unless costly slip rings are utilized within the pivotal joints of the wrench mechanism, wires from such transducers will also be exposed to the same harsh environment and therefore, may be the cause of open circuits and dead or intermittent shorts in the signal processing circuitry. Also, installation of these transducers on the wrench mechanism is an intricate task which must be laboriously repeated whenever the transducers fail or the wrench mechanism is modified or maintained.